java - 将输入从一个 JTextArea 传递到另一个 JTextArea 时遇到问题

Question

我的问题在于我的 DocumentLister AreaListener。我似乎无法弄清楚如何将用户输入的文本传递到一个 JTextArea 中进行转换，并将其返回到另一个 JTextArea。

该程序的目标是接收用户在其中一个字段中输入的罗马或阿拉伯数字，对其进行转换并将转换后的值实时返回到另一个字段。

我的 GUI 和转换方法有效，但我似乎无法全神贯注于从用户那里获取该字符串并实时打印它。

public class ArabicToRomanGUI_Hard extends JFrame
{
private static final long serialVersionUID = 1L;
 JPanel panel = new JPanel();


//constructor to add text fields to frame
public ArabicToRomanGUI_Hard()
{   
    JTextArea left = new JTextArea(10, 20);
    JTextArea right = new JTextArea(10, 20);
    setLayout(new GridLayout(1, 2));

    add(new JScrollPane(left));
    add(new JScrollPane(right));

    MirrorDocument leftDoc = new MirrorDocument();
    MirrorDocument rightDoc = new MirrorDocument();

    left.setDocument(leftDoc);
    right.setDocument(rightDoc);

    leftDoc.addDocumentListener(new DocumentHandler(rightDoc));
    rightDoc.addDocumentListener(new DocumentHandler(leftDoc));

    leftDoc.getDocument().addDocumentListener(AreaListener);
    rightDoc.getDocument().addDocumentListener(AreaListener);
   }



DocumentListener listener = new DocumentListener()

public class AreaListener implements DocumentListener
{
    //DocumentListener listener = new DocumentListener()

        @Override
        public void changedUpdate(DocumentEvent e) 
        {
            convertInput();
        }

        @Override
        public void insertUpdate(DocumentEvent e) 
        {
            convertInput();

        }

        @Override
        public void removeUpdate(DocumentEvent e) 
        {
            convertInput();

        }
        private void convertInput(DocumentEvent e)
        {
            boolean arabicEntered = false;
            boolean romanEntered = false; 
            for (char ch : userInputtedText.toCharArray())
            {
                if(Character.isLetter(ch))
                {
                    romanEntered = true;
                }
                if(Character.isDigit(ch))
                {
                    arabicEntered = true;
                }           
            }

            if(romanEntered = true)
            {
                if(ConversionLogic_Hard.getCheckFail() == false)
                {
                ConversionLogic_Hard.ConvertFromRomanToArabic(userInputtedText); //converts String of RomanNumerals to an arabic int
                String arabicNumberAsString = ConversionLogic_Hard.getConvertedRomanNumeral(); //converts number from int to string
                }
            }
            if(arabicEntered == true)
            {
                if(ConversionLogic_Hard.getCheckFail() == false)
                {
                ConversionLogic_Hard.ConvertFromArabicToRoman(userInputtedText); //converts String arabicNumberal to String roman numberal
                String romanNumberalAsString = ConversionLogic_Hard.getConvertedRomanNumeral(); //gets romanNumberal as String
                }
            }



        }//end convertInput


}//end AreaListener

//creates a flag to test the state of the TextArea
    public class MirrorDocument extends PlainDocument
    {
        private boolean ignoreUpdatedText;
        public void setIgnoreUpdates(boolean ignoreUpdatesText)
        {
            this.ignoreUpdatedText = ignoreUpdatesText;
        }
        public boolean isIgnoreUpdates()
        {
            return ignoreUpdatedText;
        }
    }

//when an event occurs checks the ignoreUpdatedText flag of the document to check if it is false.
//then sets the flag in the checkdocument to true to prevent the document listener from processing any new events.
//then updates the checkdocument.
public static class DocumentHandler implements DocumentListener
{
    private MirrorDocument checkDocument;
    private boolean ignoreUpdatedText = false;
    private JTextArea leftdoc, rightdoc;
    boolean arabicEntered = false;
    boolean romanEntered = false; 

    public DocumentHandler(MirrorDocument checkDocument)
    {
        this.checkDocument = checkDocument;
    }

    @Override
    public void removeUpdate(DocumentEvent e) 
    {
        Document doc = e.getDocument();
        if (doc instanceof MirrorDocument)
        {
            MirrorDocument mirrordoc = (MirrorDocument) doc;
            if (!mirrordoc.isIgnoreUpdates()) 
            {
                try 
                {
                    checkDocument.setIgnoreUpdates(true);
                    checkDocument.remove(e.getOffset(), e.getLength());
                } 
                catch (BadLocationException exc) 
                {
                    exc.printStackTrace();
                } 
                finally 
                {
                    checkDocument.setIgnoreUpdates(false);
                }
            }
        }   
    }//End removeUpdate

    @Override
    public void changedUpdate(DocumentEvent e) 
    {
        //NOT USED  
    }

    @Override
    public void insertUpdate(DocumentEvent e) 
    {
        Document doc = e.getDocument();
        if (doc instanceof MirrorDocument)
        {
            MirrorDocument mirrordoc = (MirrorDocument) doc;
            if( !mirrordoc.isIgnoreUpdates())
            {
                try
                {
                    String textInput = e.getDocument().getText(e.getOffset(), e.getLength());
                    checkDocument.setIgnoreUpdates(true);
                    checkDocument.insertString(e.getOffset(), textInput, null);
                }
                catch(BadLocationException exc)
                {
                    exc.printStackTrace();
                }
                finally
                {
                    checkDocument.setIgnoreUpdates(false);
                }
            }
        }
    }//End insertUpdate

    }
}//class

Answer 1

您可以使用DocumentFilter来监听更改。

创建DocumentFilter时，您可以指定要使用转换后的文本更新的文本字段。

使用这种方法，您可以在设置文本字段之前从文本字段中删除 DocumentFilter，这样就可以避免两个文本字段尝试相互更新的递归情况。

过滤器可能看起来像:

import javax.swing.*;
import javax.swing.text.*;
import java.awt.Toolkit;

public class ConversionFilter extends DocumentFilter
{
    private boolean arabic;
    private JTextField converted;

    public ConversionFilter(boolean arabic, JTextField converted)
    {
        this.arabic = arabic;
        this.converted = converted;
    }

    @Override
    public void insertString(FilterBypass fb, int offs, String str, AttributeSet a)
        throws BadLocationException
    {
        super.insertString(fb, offs, str, a);

        convertInput(fb);
    }

    @Override
    public void replace(final FilterBypass fb, final int offs, final int length, final String str, final AttributeSet a)
        throws BadLocationException
    {
        super.replace(fb, offs, length, str, a);
        convertInput(fb);
    }

    @Override
    public void remove(DocumentFilter.FilterBypass fb, int offset, int length)
        throws BadLocationException
    {
        super.remove(fb, offset, length);
        convertInput(fb);
    }

    private void convertInput(DocumentFilter.FilterBypass fb)
    {
        //  Remove the DocumentFilter from the text field to be converted

        AbstractDocument document = (AbstractDocument)converted.getDocument();
        DocumentFilter df = document.getDocumentFilter();
        document.setDocumentFilter( null );

        //  Do the conversion and update the text field

        String text = fb.getDocument().getText();
        String convertedText = arabic ? convertToRoman(text) : convertToArabic(text);
        converted.setText( convertedText );

        //  Restore the DocumentFilter on the converted text field

        document.setDocumentFilter( df );
    }
}

然后要使用过滤器，代码可能类似于:

JTextField arabicTextField = new JTextField(...);
JTextField romanTextField = new JTextField(...);

AbstractDocument arabicDocument = (AbstractDocument)arabicTextField.getDocument();
arabicDocument.setDocumentFilter( new ConversonFilter(true, romanTextField) );

AbstractDocument romanDocument = (AbstractDocument)romanTextField.getDocument();
romanDocument.setDocumentFilter( new ConversonFilter(false, arabicTextField) );

我使用 DocumentFilter 而不是 DocumentListener 来接收文档更改的通知，只是因为 DocumentFilter 的 getter/setter 方法很容易删除和恢复过滤器。